020 is the national dialling code for London in the United Kingdom. All subscriber numbers within the area code consist of eight digits and it has capacity for approaching 100 million telephone numbers. The code is used at 170 telephone exchanges in and around Greater London as part of the largest

linked numbering scheme A linked numbering scheme (LNS) is a dialing procedure in effect in a service area within which call routing between adjacent exchanges does not require a dialing code. The term is only used in the United Kingdom, but not in the North American ...

in the United Kingdom. In common with all other British area codes the initial '0' is a

trunk prefix A trunk prefix is a digit sequence to be dialed before a telephone number to initiate a telephone call for the purpose of selecting an appropriate telecommunications circuit by which the call is to be routed. Making a domestic (national) telephone ...

that is not required when dialling London from abroad. The 020 area code fully replaced older area codes for London on 22 April 2000, following multiple telephone number changes during the 1990s.020 could be used from 1 June 1999 and the previous 0171 and 0181 codes could no longer be used from 22 April 2000. As is the case for other codes in the UK, the 020 area code may also be used for services without any physical presence in the area, such as private networks or virtual numbering. As one such user is the Foreign and Commonwealth Office Telecommunications Network, provided by

Global Crossing Global Crossing was a telecommunications company that provided computer networking services and operated a tier 1 carrier. It maintained a large backbone network and offered peering, virtual private networks, leased lines, audio and video con ...

, 020 is also one of the dialling codes used for telephone services on the remote South Atlantic island of

Tristan da Cunha Tristan da Cunha (), colloquially Tristan, is a remote group of volcanic islands in the South Atlantic Ocean. It is the most remote inhabited archipelago in the world, lying approximately from Cape Town in South Africa, from Saint Helena a ...

History

London telephone area

Before the introduction of national dialling codes, the area now served by 020 had a large multiple telephone exchange system, called the London telephone area. The first exchange in this area, Central, was opened in the

City of London The City of London is a city, ceremonial county and local government district that contains the historic centre and constitutes, alongside Canary Wharf, the primary central business district (CBD) of London. It constituted most of London f ...

on 1 March 1902. The

Director telephone system The director telephone system was a development of the Strowger or step-by-step (SXS) switching system used in London and five other large cities in the UK from the 1920s to the 1980s. A large proportion (c. 70% to 80%) of telephone traffic in ...

was developed so that subscribers in London could call one another in a

regardless of whether they were on a manual local exchange or an automatic one. In 1927, Holborn, the first

Director Director may refer to: Literature * ''Director'' (magazine), a British magazine * ''The Director'' (novel), a 1971 novel by Henry Denker * ''The Director'' (play), a 2000 play by Nancy Hasty Music * Director (band), an Irish rock band * ''D ...

automatic exchange in London, was cut over to the new system at midnight on Saturday 12 November. Because it was mainly a business exchange, most subscribers did not use the new system until Monday 14 November. The successful changeover was delayed by subscribers' unfamiliarity with dialling. Bishopgate and Sloane exchanges followed in six weeks, after which came Western and Monument exchanges. Because the London area contained 80 exchanges, complete conversion took many years.The Times (London), 1927; 14 November p9 & 16 November p9 By 1934, the London telephone area comprised all 147 exchanges within of Oxford Circus. By 1950, the London Director system had 75 exchanges within a radius of Oxford Circus and a further 65 in the 5–10-mile (8–16 km) belt. In Greater London (in other words, within of Oxford Circus), there were 237 exchanges. In January 1956 a new director exchange – "SKYport" – was opened at

London Heathrow Airport Heathrow Airport (), called ''London Airport'' until 1966 and now known as London Heathrow , is a major international airport in London, England. It is the largest of the six international airports in the London airport system (the others be ...

Exchange codes

From 1922, the first three digits of a seven-digit subscriber numberin other words, the local exchange codeswere represented with letters by way of a

mnemonic A mnemonic ( ) device, or memory device, is any learning technique that aids information retention or retrieval (remembering) in the human memory for better understanding. Mnemonics make use of elaborative encoding, retrieval cues, and imag ...

. Each three-character code corresponded to an exchange within the London telephone area. The subscriber numbers were written, for example, as "ABBey 1234" and "WIMbledon 1234" or "ABB 1234" and "WIM 1234". By 1965, there were 350 local exchanges in London and the number of permutations that could be used for exchange names had been exhausted. With the change to all-figure dialling in 1966, the system of mnemonics was withdrawn and the three-digit local exchange codes of many subscribers were altered. The old codes continued to work in parallel with new codes until January 1970, when the "ANN: All-figure Numbers Now" advertising campaign prompted callers to use only the new codes. The transition to all-figure dialling allowed the codes to be grouped into eight sectors; all exchanges within of the centre of London formed the Central sector and the other sectors radiated from it. The first three digits of a subscriber number continued to indicate the exchange to which the number belonged; for example, "222 1234" was in Westminster (Central Sector) and "946 1234" in Wimbledon (South West Sector).The numerical codes for Westminster and Wimbledon did not change when all-figure dialling was introduced because the first two digits of their exchange codes corresponded to the sectors they became part of. More than one local exchange code was usually overlaid for each area, so all Wimbledon numbers did not necessarily begin "946". Subscriber numbers changed to eight digits in 2000 when an additional 7 or 8 was added to each local exchange code (for example, "7222 1234" in Westminster and "8946 1234" in Wimbledon).

STD code

The

STD code Subscriber trunk dialling (STD), also known as subscriber toll dialing, is a telephone numbering plan feature and telecommunications technology for the dialling of trunk calls by telephone subscribers without the assistance from switchboard oper ...

01 was assigned to the London telephone area on 6 April 1959 as part of preparations for subscriber trunk dialling. For the next thirty years, "01" became synonymous with the capital.For example, in the name of the cultural show ''

01-for London ''01-for London'' was a Thames Television programme broadcast on ITV in South-East England between 1987 and 1992. It was a weekly arts listings programme developed in conjunction with ''Time Out'' magazine. The programme was produced by Tom G ...

'', broadcast by

Thames Television Thames Television, commonly simplified to just Thames, was a franchise holder for a region of the British ITV television network serving London and surrounding areas from 30 July 1968 until the night of 31 December 1992. Thames Television broa ...

between 1987 and 1990 (). Until May 1990, the 01 code covered the same area as the current 020 code and had capacity for fewer than 10 million telephone numbers. In May 1990, the 01 code was abandoned and the area divided between 071which covered exchanges in the Central sectorand 081, which covered all other sectors. Exceptionally, two exchanges in the East sectorAlbert Dock and Poplar exchanges were not in the Central sector but were included in the 071 code. covering the London Docklands redevelopment area were assigned the 071 code. The anticipation that the code associated with central districts would be more prestigious than the other associated with the outer suburbs was used as a plot device in the Essex-based TV comedy series '' Birds of a Feather''. At the time of the split, there were five local exchange codes assigned to

Mercury Communications Mercury Communications was a national telephone company in the United Kingdom, formed in 1981 as a subsidiary of Cable & Wireless, to challenge the then-monopoly of British Telecom (BT). Although it proved only moderately successful at challe ...

Exchange codes 528, 895, 945, 975 and 982 were assigned to Mercury Communications. and numbers in these ranges could be assigned to either code. This area code split doubled the potential capacity. In 1995, on "

PhONEday PhONEday was a change to the telephone dialling plan in the United Kingdom on 16 April 1995. It changed geographic area codes and some telephone numbers. In most areas, a "1" was added to the dialling code after the initial zero. In Bristol, Le ...

", the codes changed again, to 0171 and 0181. History of London STD codes

The split into two area codes only lasted a decade. As part of the

Big Number Change The Big Number Change addressed various issues with the telephone dialling plan in the United Kingdom, during the late-1990s and early-2000s. The first was an update to a small number of geographic dialling codes in response to the rapid late-19 ...

on 22 April 2000, the 0171 and 0181 codes were replaced with 020, following a period of dual-running that began on 1 June 1999 when the new 020 code was activated and ended on 14 October 2000 when the old 0171 and 0181 codes were finally ceased. The 22 April 2000 change also affected subscriber local numbers which gained an extra digit. "0171-xxx xxxx" numbers changed to "(020) 7xxx xxxx", while "0181-xxx xxxx" numbers became "(020) 8xxx xxxx". As a result of this history, there is now a widespread misconception that 0207 and 0208 are the dialling codes for parts of London. This was exacerbated when local numbers beginning 3 started to be issued. The reunification under a single code created capacity for approaching 100 million telephone numbers and, starting in 2005, subscriber numbers beginning with the digit "3" were issued alongside those beginning "7" and "8". In August 2019, Ofcom announced that subscriber numbers beginning with the digit "4" will also be introduced.

Charge group

The London telephone area operated as a single group for charging purposes in which all calls were priced at local rate. Additionally, as was usual, calls to and from the adjacent charge groups were charged as local.Calls to London from each of the 01322, 01372, 01689, 01707, 01708, 01727, 01737, 01753, 01784, 01883, 01895, 01923, 01932, 01959 and 01992 area codes were charged at local rate, as were calls from London to each of those area codes.

Coverage

The code serves a roughly circular area with a radius of from the centre of London. The Greater London boundary varies from to from the centre and consequently some outer districts are covered by adjacent codes and in some places the 020 code extends beyond the Greater London boundary. The code covers an area larger than the London post town where letters addressed to "LONDON" are delivered. The

and at least some part of all 32

London borough The London boroughs are the 32 local authority districts that together with the City of London make up the administrative area of Greater London; each is governed by a London borough council. The present London boroughs were all created at ...

s are within the 020 area code. There are six exchanges outside Greater London that use the 020 code.Bushey Heath, Elstree, Ewell, Hainault (Chigwell), Loughton and Thames Ditton exchanges are outside Greater London. Communities outside Greater London that are within the code are

Buckhurst Hill Buckhurst Hill is an affluent suburban town in the Epping Forest district of Essex, England. It is part of the Greater London Urban Area and adjacent to the northern boundary of the London Borough of Redbridge. The area developed following the o ...

Chigwell Chigwell is a town and civil parish in the Epping Forest District of Essex, England. It is part of the urban and metropolitan area of London, and is adjacent to the northern boundary of Greater London. It is on the Central line of the Lond ...

Loughton Loughton () is a town and civil parish in the Epping Forest District of Essex. Part of the metropolitan and urban area of London, the town borders Chingford, Waltham Abbey, Theydon Bois, Chigwell and Buckhurst Hill, and is northeast of Chari ...

and

Sewardstone Sewardstone is a hamlet and district of southern Waltham Abbey, in the Epping Forest District of Essex, England, lying between Epping Forest and the built-up areas of Waltham Abbey, Chingford and Enfield. It is 11.6 miles north-northeast of Cent ...

in Essex;

Borehamwood Borehamwood (, historically also Boreham Wood) is a town in southern Hertfordshire, England, from Charing Cross. Borehamwood has a population of 31,074, and is within the London commuter belt. The town's film and TV studios are commonly know ...

Bushey Bushey is a town in the Hertsmere borough of Hertfordshire in the East of England. It has a population of over 25,000 inhabitants. Bushey Heath is a large neighbourhood south east of Bushey on the boundary with the London Borough of Harrow ...

, Carpenders Park,

Elstree Elstree is a large village in the Hertsmere borough of Hertfordshire, England. It is about northwest of central London on the former A5 road, that follows the course of Watling Street. In 2011, its population was 5,110. It forms part of t ...

and

South Oxhey South Oxhey is a suburb of Watford in the Watford Rural parish of the Three Rivers district of Hertfordshire, England. It is located in the south western corner of Hertfordshire and close to the boundary with Greater London. At the 2011 Census S ...

in Hertfordshire; and

Ewell Ewell ( , ) is a suburban area with a village centre in the borough of Epsom and Ewell in Surrey, approximately south of central London and northeast of Epsom. In the 2011 Census, the settlement had a population of 34,872, a majority of wh ...

Molesey Molesey is a district of two twin towns, East Molesey and West Molesey, in the Borough of Elmbridge, Surrey, England, and is situated on the south bank of the River Thames. East and West Molesey share a high street, and there is a second retai ...

Thames Ditton Thames Ditton is a suburban village on the River Thames, in the Elmbridge borough of Surrey, England. Apart from a large inhabited island in the river, it lies on the southern bank, centred 12.2 miles (19.6 km) southwest of Charing Cross ...

and

Whyteleafe Whyteleafe is a village in the district of Tandridge, Surrey, England, with a few streets falling inside the London Borough of Croydon. The village, in a dry valley of the North Downs, has three railway stations (on two parallel lines). Neighbouri ...

in Surrey. There are eighteen exchanges within Greater London that do not use the 020 code.Biggin Hill, Crayford, Denham, Downland, Erith, Farnborough, Harefield, Hornchurch, Ingrebourne, Lodge Hill, Northwood, Orpington, Rainham, Romford, Ruislip, Slade Green, Upminster, Uxbridge and West Drayton do not use the 020 code. The six boroughs that have significant areas within other codes are

Bexley Bexley is an area of south-eastern Greater London, England and part of the London Borough of Bexley. It is sometimes known as Bexley Village or Old Bexley to differentiate the area from the wider borough. It is located east-southeast of Ch ...

, partly within the Dartford (01322) code;

Bromley Bromley is a large town in Greater London, England, within the London Borough of Bromley. It is south-east of Charing Cross, and had an estimated population of 87,889 as of 2011. Originally part of Kent, Bromley became a market town, c ...

, partly within the Orpington (01689) and Westerham (01959) codes;

Croydon Croydon is a large town in south London, England, south of Charing Cross. Part of the London Borough of Croydon, a local government district of Greater London. It is one of the largest commercial districts in Greater London, with an extensi ...

, partly within the Orpington (01689) and Redhill (01737) codes;

Enfield Enfield may refer to: Places Australia * Enfield, New South Wales * Enfield, South Australia ** Electoral district of Enfield, a state electoral district in South Australia, corresponding to the suburb ** Enfield High School (South Australia) ...

, partly within the Waltham Cross (01992) code;

Havering The London Borough of Havering () in East London, England, forms part of Outer London. It has a population of 259,552 inhabitants; the principal town is Romford, while other communities are Hornchurch, Upminster, Collier Row and Rainham. The ...

, mostly within the Romford (01708) code; and

Hillingdon Hillingdon is an area of Uxbridge within the London Borough of Hillingdon, centred 14.2 miles (22.8 km) west of Charing Cross. It was an ancient parish in Middlesex that included the market town of Uxbridge. During the 1920s the civ ...

, partly within the Uxbridge (01895), Slough (01753) and Watford (01923) codes.

Number allocation

With the introduction of the (020) area code, as part of the

, subscriber numbers were changed from 7-digits (xxx xxxx) to 8-digits (xxxx xxxx). This allowed new ranges of numbers to be issued. Under the

National Telephone Numbering Plan Telephone numbers in the United Kingdom are administered by the Office of Communications ( Ofcom). For this purpose, Ofcom established a telephone numbering plan, known as the ''National Telephone Numbering Plan'', which is the system for ass ...

the code operates with the following sub-ranges: In 2006 59% of numbers within the 020 code were allocated to BT. The area code is not subject to number conservation and the regulator Ofcom does not restrict the size of number blocks that are allocated.

Notes

References

External links

List of exchanges in 1966

Number allocations
{{Telephone numbers in the United Kingdom 20 Infrastructure in London